SAN FRANCISCO (AP), Mar 16 - State regulators were expected to decide as soon as Wednesday how they would sanction the California utility under fire for a deadly explosion on a natural gas pipeline, segments of which the company said it was missing key safety records.

Among the options that the California Public Utilities Commission could consider was whether to require Pacific Gas & Electric Co. to conduct expensive, time-consuming tests on its transmission lines, which run through some of the state's most populated areas. It also has said levying fines was a possibility.

The Sept. 9 blast sparked a massive fireball that killed eight people and destroyed three dozen homes in San Bruno, a quiet suburb overlooking the San Francisco Bay.

Almost immediately after the explosion, regulators ordered PG&E to provide detailed safety updates, including information about how the utility was prioritizing work on high-risk lines during the next four years. After an exhaustive document search, which involved the company renting a hulking concert venue for employees to sift through mountains of paper records, PG&E announced Tuesday that it was missing 8 percent of key safety records required for its high-pressure pipelines.

PG&E spokesman Joe Molica also confirmed that the company could not find paperwork on pressure tests for some sections of Line 132 - the pipeline in the San Bruno explosion - but he did not immediately clarify in which cities those segments lay.

PG&E released its results after the massive search, which has spanned the past two weeks. Company engineers, estimators, mappers, information technology specialists and managers - as well as a number of outside contractors - went through more than 1.25 million individual gas transmission records hauled out from branch offices and storage facilities.

Overall, 10 percent of aging lines installed before 1961 were missing test records or other documents showing historical pressure levels, as were 3 percent of the lines laid from 1961 to 1970, PG&E found.

``While we have made good progress on our records validation, we are not satisfied with the results to date and will continue to search for and review our files for additional pressure test records and provide regular updates on our efforts,'' utility president Chris Johns said in a statement.

He said the company planned to pressure-test or replace 150 miles of pipe that is either as old as the San Bruno line or has other similar characteristics. The work will be carried out across 24 pipelines, he said, including on a segment of the ruptured line.

The company also will carry out rigorous inspections on another 435 miles of pipe, in which robotic devices called ``smart pigs'' will travel through pipelines to search for corrosion, dents and other problems, he said.

Federal investigators have been questioning PG&E's record-keeping since December, when the National Transportation Safety Board first revealed the company's records about the 1956-era pipe were wrong.

The pipeline was riddled with seams, defects and inferior welds, although PG&E paperwork inaccurately identified the pipe as being seamless, which is considered safer.

In January, the state commission directed PG&E and other California utilities to produce records documenting the safety of all their lines.

State rules require pipeline operators to keep up-to-date records about pressure tests and to document any leaks to ensure the pipes don't pose a risk to surrounding communities.

Consumer advocates said customers deserved to know more details about where the lines with no records were located, and whether the company had been operating them safely.

``Ninety-two percent sounds pretty good unless you happen to live over the 8 percent that they don't have records for,'' said Mark Toney, executive director of San Francisco-based The Utility Reform Network. ``I think that people are going to be interested in knowing where that 8 percent is.''

Rep. Jackie Speier, a California Democrat who represents the San Bruno area, said she was pleased at the advances since the explosion, but questioned PG&E's reliance on documents detailing historical pressure levels. She said that would not necessarily identify improper welds or shoddy work on the pipes.

``If you're just saying that you have five years of records showing what the pressure was over time, I don't know whether that means the level is safe,'' said Speier. ``We now know that the San Bruno pipe was seamed, had a defective weld and probably other problems.''

The commission was likely to vote on the proposed decision requiring PG&E to send out more frequent safety updates next month.